Review of Supercritical Gas Extraction Applications to Coal Conversion Processes

Abstract

The applications of supercritical gas extraction are reviewed for refining, deashing and deasphalting of coal and coal derived liquids. After the prin-ciples and characteristics of supercritical gas extraction are stated, it is shown how the extraction yield and the features of extracts and/or raffinates are affected by the extraction conditions (extraction temperature and pressure, coal type and solvent type).
The extraction yield of coal becomes larger as the H/C value of coal, hydrogen donor ability of the solvent, extraction temperature and pressure increase. Temperature is considered to be the most effective factor for increasing extraction yield from flow type experimental studies.The efficiency of deashing and deasphalting of coal derived liquids is affected mainly by the extraction temperature and changes drastically near the critical temperature of solvent.
Supercritical gas extraction offers considerable potential as an alternative to con-version processing of coal and coal derived liquids.